Keratinocytes, the predominant cells of the epidermis, provide on one hand mechanical protection and on the other participate in immunological defense as well. The immunological protection is provided in part by keratinocyte activation, which appears in pathological conditions, such as wound healing, allergic and inflammatory reactions. In response to epidermal injury, keratinocytes become "activated", produce and respond to growth factors and cytokines, become migratory and produce components of the basement membrane. In activated keratinocytes keratins K#5 and K#14 are replaced by hyperproliferation/activation-specific keratins K#6 and K#16, which can be considered activation-specific markers. The hypothesis that forms the basis for this proposal states that the choice of which keratin proteins will be expressed by a keratinocyte is determined, in part, by the polypeptide growth factors and cytokines that determine the cell phenotype. This hypothesis is confirmed by the preliminary results. The aims of this proposal are to determine the molecular mechanisms by which the peptide factors that modulate keratinocyte activation and differentiation, in particular EGF, TGFbeta and interferon gamma, regulate expression of keratin genes. Specifically, the aims are to: determine the effects on transcription of keratin genes of these three polypeptide factors, map the DNA sequences in the keratin genes responsible for the effects of polypeptides, characterize the nuclear proteins acting on those sequences, and correlate the function of those nuclear proteins with keratin gene expression in normal skin and in pathological conditions. The experiments follow a common path: from identification of the effects of a polypeptide growth factor on keratin gene expression, to characterization of the corresponding transcription factor, followed by purification and cloning of the transcription factor, antibody production and finally analysis of transcription factor interactions and their role in epidermal diseases. These experiments are very important because they will lead to knowledge of transcriptional interactions at the molecular level in the nucleus among the polypeptide growth factors that change keratinocyte physiology.